Overview
Ultrafiltration (UF) equipment is a separation device based on ultrafiltration membrane technology, which efficiently intercepts macromolecules, colloids, microorganisms, suspended particles, and other impurities in fluids through the selective sieving effect of membrane elements. Its core principle uses pressure driving (typically 0.1–0.6 MPa) to force fluids through ultrafiltration membranes with pore sizes of 0.001–0.1 μm, retaining substances with molecular weights ranging from 1,000 to 300,000 Daltons, while allowing water and small molecular solutes to pass through smoothly. Widely used in drinking water purification, industrial wastewater treatment, food and beverage processing, biomedical separation, seawater desalination pretreatment, and other fields, this equipment features high separation efficiency, low energy consumption, and simple operation, making it one of the core technologies in modern water treatment and fluid separation.
Working Principle
I. Fluid Pretreatment
The fluid to be treated (such as water, emulsions, or process liquids) first undergoes coarse filtration (e.g., 10–50 μm filter elements) to remove large particulate impurities and prevent membrane pore blockage. For oily or high-viscosity fluids, pH adjustment or dispersant addition may be required to improve fluid properties and enhance membrane flux and service life.
II. Ultrafiltration Membrane Separation Process
1. Pressure-Driven Sieving Mechanism:
The pretreated fluid is pumped into the ultrafiltration membrane module. Under the pressure difference across the membrane, water molecules and small molecules (e.g., inorganic salts, monosaccharides) pass through the membrane pores to form the permeate (product water), while macromolecules (e.g., proteins, colloids, bacteria) are retained to form the concentrate (brine).
2. Cross-Flow Filtration Design:
The fluid flows laterally across the membrane surface at high speed (1–5 m/s) in a cross-flow state, reducing impurity deposition on the membrane surface and minimizing concentration polarization to maintain stable filtration flux.
III. Cleaning and Maintenance
As filtration progresses,intercepts (retentate) such as colloids and organic matter accumulate on the membrane surface, causing flux decline. Membrane performance is restored through:
- Physical Cleaning: Backwashing with water or air-water mixture to remove surface contaminants, typically performed every 30–120 minutes.
- Chemical Cleaning: Using acids (e.g., citric acid), alkalis (e.g., NaOH), or specialized cleaning agents to dissolve stubborn contaminants, usually conducted 1–3 times per month.
Performance Characteristics
I. Efficient Separation and Precise Retention
- Broad Adaptability: Capable of retaining bacteria (e.g., E. coli, 0.5–3 μm), viruses (e.g., bacteriophages, 20–30 nm), colloids (e.g., Fe(OH)₃, 1–100 nm), and macromolecular organics (e.g., starch, proteins), suitable for separating impurities from the microscale to nanoscale.
- High Flux and Low Energy Consumption: Water flux reaches 50–200 L/(m²·h) with energy consumption of only 0.1–0.3 kWh/m³, far lower than reverse osmosis (RO) and evaporation processes.
II. Modular and Flexible Configuration
- Diverse Membrane Modules:
- Hollow Fiber Membranes: Internal or external pressure types with high packing density (1,000–3,000 m²/m³), suitable for large-scale water treatment.
- Spiral Wound Membranes: Compact structure for high-concentration liquid separation.
- Tubular/Flat Sheet Membranes: Strong anti-fouling capability for suspended solids or high-viscosity fluids.
- Scalable Systems: Parallel membrane modules or multi-stage series configurations can increase throughput or separation precision, catering to needs from small laboratories (0.5 m³/h) to large water plants (10,000 m³/h).
III. Long Lifespan and Low Maintenance
- Membrane Element Lifespan: 3–5 years under normal conditions; ceramic ultrafiltration membranes can last over 10 years.
- Intelligent Operation and Maintenance: Integrated online monitoring (flow, pressure, turbidity) and automatic cleaning systems reduce manual intervention and lower O&M costs by 30%–50%.
IV. Environmentally Friendly
- Chemical-Free Process: Pure physical separation eliminates the need for flocculants or desalination chemicals, avoiding secondary pollution.
- Resource Recovery: Concentrates can be further processed to recover valuable substances (e.g., proteins in dairy, precious metals in wastewater), promoting circular economy.
Structural Components
I. Membrane Modules
- Membrane Elements: The core component, composed of ultrafiltration membranes (materials include PVDF, PS, ceramics, etc.) and support structures, determining separation precision and flux.
- Pressure Vessels: House membrane elements, made of stainless steel or FRP, with pressure resistance of 0.6–1.0 MPa.
II. Pump and Pipeline System
- Feed Pump: Provides filtration pressure, commonly centrifugal or screw pumps.
- Recirculation Pump: Maintains fluid velocity in cross-flow filtration to reduce membrane fouling.
- Valve Set: Includes feed, product, concentrate, and cleaning valves for process switching and flow regulation.
III. Control System
- PLC Control Cabinet: Integrates pressure sensors, flow sensors, and online turbidity meters to monitor operating parameters in real time.
- Human-Machine Interface (HMI): Sets cleaning cycles, pressure thresholds, etc., supporting remote monitoring (e.g., IoT integration).
IV. Auxiliary Equipment
- Cleaning Water Tank: Stores cleaning fluids (water, acid, alkali) with a dedicated cleaning pump.
- Security Filter (Security Filter): 5–20 μm filter elements protect membrane elements from large particle damage.
Application Cases
I. Advanced Drinking Water Treatment
- Shanghai Qingcaosha Reservoir Pretreatment
Qingcaosha Reservoir uses hollow fiber ultrafiltration membranes as RO pretreatment, with an 800,000 m³/day treatment capacity. It截留 (retains) algae, colloids, and macromolecular organics, with product water turbidity <0.1 NTU, ensuring stable RO system operation. Energy consumption is only 0.08 kWh/ton, 40% less than traditional processes.
- Baiyangdian Ecological Water Supply, Xiongan New Area
The Baiyangdian water replenishment project employs ceramic ultrafiltration membranes to treat slightly polluted water, achieving removal rates of 45% for COD, 30% for ammonia nitrogen, and 99% for algae. The product water meets Class III standards of *Environmental Quality Standards for Surface Water* (GB3838), supporting ecological restoration in Xiongan.
II. Industrial Wastewater Reuse
- Acid-Base Wastewater Treatment in Electronics Factories
A semiconductor factory uses acid-alkali-resistant ultrafiltration membranes to treat wastewater containing HF and H₂SO₄, retaining photoresist particles (>0.1 μm) and heavy metal ions (e.g., Cu²+, Ni²+). The product water is reused for cleaning with a reuse rate >85%, saving over ¥5 million annually in water costs.
- Textile Dyeing Wastewater Decolorization
A Shaoxing dyeing mill uses polysulfone ultrafiltration membranes to treat dyeing wastewater, achieving 85% color removal (initial >3,000 times) and 60% COD removal (>1,000 mg/L), reducing the load on subsequent biochemical treatment. The product water is reused for workshop flushing, saving 200,000 tons of water annually.
III. Food and Biomedical Applications
- Whey Protein Concentration
Yili Dairy uses 100k Da ultrafiltration membranes to concentrate whey, increasing protein concentration from 5% to 35% while retaining lactose and minerals. Energy consumption is 75% lower than thermal concentration, and by-product whey permeate is used for low-lactose milk production.
- Vaccine Clarification and Purification
Sinovac uses tangential flow filtration (TFF) ultrafiltration membranes in COVID-19 vaccine production to remove cell debris and virus-like particles (VLPs) with >99.9% retention efficiency, while concentrating viruses and reducing downstream chromatography column loads, increasing production capacity by 30%.
IV. Seawater Desalination Pretreatment
- Jubail Seawater Desalination Plant, Saudi Arabia
The Jubail II project uses PVDF ultrafiltration membranes as RO pretreatment with a 1,000,000 m³/day capacity, producing water with SDI <3 and stable membrane flux at 60 L/(m²·h). Combined with energy recovery devices, total energy consumption is <3 kWh/ton, a global benchmark.
- South China Sea Island Water Supply
An island reef employs anti-fouling ultrafiltration membranes to treat high-turbidity seawater (turbidity >50 NTU), equipped with an automatic backwashing system. The product water meets domestic water standards, solving operational challenges of traditional processes in complex water quality.
Conclusion
Ultrafiltration equipment has become a core fluid separation solution across industries due to its efficiency, energy savings, and flexibility. From precision purification of urban drinking water to circular reuse of industrial wastewater, and from component retention in food processing to precision separation in vaccine production, ultrafiltration technology continues to expand its application boundaries through material innovations (e.g., ceramic membranes, composite nanofilms) and intelligent upgrades (e.g., AI predictive maintenance). With the advancement of global "double carbon" goals, ultrafiltration equipment will play a more critical role in water resource recycling and high-end manufacturing, driving the world toward sustainable development.
